Light sources are used in endoscopy to inspect regions within a body during surgery. Typically, an endoscope includes a rigid or flexible elongate insertion tube equipped with a set of optical fibers that extend from a proximal handle through the endoscope body to a distal viewing tip thereof. An external light source provides light to the optic fibers via a cable that attaches to a post on a side of the endoscope. In some embodiments, the endoscope includes an imaging device for providing a image to a monitor for viewing by a surgeon.
Prior art FIGS. 1 and 2 are taken from U.S. Pat. No. 6,921,920, which discloses a solid state light source. As illustrated in FIG. 1, an endoscopic system 10 for providing illumination can include a solid-state light source 12, a video monitor 14, a camera 16, and endoscope 18. The light source 12 generates white light that is conveyed to a distal end 22 of the endoscope 18 via a light guide 26. The light guide 26 includes multiple fibers and is connected between an output connector 28 of the light source 12 and a light post 30 of the endoscope 18. The white light illuminates a working area 24 at the distal end 22 of the endoscope. The video camera 16, connected to a handle 32 of the endoscope generates video signals representative of images at the working area 24 for display on video monitor 14.
FIG. 2 shows a schematic of a specific light source 12 for the known arrangement of FIG. 1. The light source 12 of FIG. 2 includes an optical system 34 and a lens array 36 used to collimate light from a corresponding LED array 38. A focusing lens 40 then focuses the light onto a light guide 52.
LED array 38 is arranged in a circular-shaped 2-dimensional array. Corresponding lens array 36 is located in front of the LED array 38 so that each semi-conductor light source 42 is positioned along an optical axis 44 of the corresponding lens 46. Lenses 46 collimate light emitted by their corresponding LEDs 42. Lenses 46 may represent single lenses, such as single or double aspherics, compound lenses, radiant index type lenses or combinations of each. Other arrangements have lens arrays that are implemented as part of an LED array by adhesion, fusion or the like. Some arrangements have a rectangular shaped LED and lens array.
The focal length of the lens 40, and the diameter of the lenses 46 are chosen on the order of a few millimeters. The actual values are selected based on the size of LED emitting surface 48 which determines the field of view of the lens 46.
The collimated light from lens array 36 travels to the focusing lens 40. Focusing lens 40 projects the image of each LED light emitting surface 48 onto an entrance face 50 of the light guide 42. The image is magnified so that the size is approximately equal to the size of the entrance face 50 of the light guide 42. The light guide 42 transports the light to an endoscope. The light passes through the endoscope to illuminate a surgical site. Camera 16 provides images of the surgical site for display on video monitor 14.
An area of concern with the above described endoscopic system and other endoscopic illuminating systems is the transfer of heat from a light source through the light guide 26 to a metal junction at the distal end of the scope. In some instances, the temperature at the distal end of the scope can be as high as 70° C. If a surgeon removes the endoscope from within a patient and places the endoscope on their body, burning of the skin of a patient may occur. Further, when the endoscope is disposed inside the body of a user, there is a possibility that the metal distal tip will injure tissue of the patient.
One object of the invention is to provide an apparatus having a plurality of solid state light sources that are operated at a minimal voltage or power level while providing a necessary amount of light.
One embodiment of the invention is to sense the color of light applied through an endoscope to the surgical site. Depending on the sensed color values, the power to individual light emitting diodes or diode arrays is controlled to balance the colors of light to result in a white light. In this way, white balance in a camera receiving reflected light from the light source is not as necessary as compared to light sources having no color balance feedback.
Another embodiment of the invention automatically stops providing power to the light source when the distal end of the fiber optic cable is disconnected from the endoscope.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement, and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.